Matched Correlation of linear and non-linear frequency-modulated waveforms for far-field TDOA-DoA in the context of MFRFS

In the context of “Waveform Diversity” this paper presents a comparison between linear frequency modulated waveforms and non-linear frequency-modulated waveforms for dual-channel time difference of arrival (TDOA) applications to estimate the direction of arrival (DoA) of an impinging planar wavefront. Non-linear frequency-modulated waveforms are well suited for the determination of TDOA by cross-correlation due to their correlation properties with respect to their reduced sidelobes compared to linear frequency modulated chirps. The waveforms are examined for customized dual-channel processing consisting of matched filtering of the individual receive channels and subsequent cross-correlation of the matched filter outputs. This kind of processing is especially suitable for signal-to-noise ratios below 0 dB. This enables two-channel e.g. electronic support measures (ESM) receivers or a distributed arrangement of receiver nodes to perform direction of arrival estimation at low signal powers and with only two receive paths. The presented results show clear robustness at low signal-to-noise ratios using non-linear frequency modulation compared to linear frequency modulated chirps and the standard cross-correlation to determine the time offset.